196
P.L. Tyack and c.w. Clark
and Vehrencamp 1998). Catchpole (1982) suggests that continuous singing,
lack of matched counter-singing between males, and lack of a singing
response to song playback are also diagnostic of a female attraction role
for song. Humpback whales often sing continually for hours, they do not
respond to the song of another male by immediately matching the sounds
produced by the male, nor do they respond to song playbacks by singing
themselves. These features are consistent with the hypothesis that humpback males sing in part to influence the mating choices of females. Humpback songs have several features that suggest that males are attending to
the songs of other males: they are acoustically elaborate, singers within a
population sing similar songs at anyone time, and males constantly change
their songs over the course of the breeding season. For singers to track all
these myriad changes, they must be attending to many subtle features of
the songs of other whales.
3.2.2 Balaenid Whales: Bowhead and Right Whales
Baleen whales other than humpback whales have also been reported to
produce reproductive advertisement displays. Bowhead whales, B. mysticetus, have been recorded producing songs as they migrate from their breeding grounds (Ljungblad et al. 1982; Clark 1988, 1991a; Wiirsig and Clark
1993). These whales spend their winter breeding season in arctic waters such
as the Bering Sea, where it is difficult to observe them, so we know little
about behavior during the peak of the breeding season. While the individual sounds that make up bowhead songs are somewhat similar to those of
humpbacks, bowhead songs have a simpler structure, consisting of a single
trill of repeated, multi-unit phrases followed by a trill of repeated, singleunit phrases. Bowhead songs are also shorter than humpback song, lasting
a minute or so. The songs of bowhead whales share an unusual feature with
the songs of humpback whales: they change from year to year. An unusual
feature of bowhead song is that it is composed of two voices that are harmonically unrelated yet often simultaneous. Figure 4.10 shows bowhead
songs of the Bering-Chukchi-Beaufort Seas population from four different
years recorded during the spring migration off Point Barrow, Alaska. The
communicative function of songs during migration is unknown. The following observations suggest that spring song of migrating whales may be a
vestige at the end of the winter breeding season: (1) this singing is only
recorded during the first weeks of the migration when the migration is dominated by adult males and small adults, (2) spring song is infrequent, and
(3) spring song is limited to bouts lasting only a few hours.
The great majority of sounds produced by bowhead whales during the
spring migration off Point Barrow, Alaska, are calls (Clark and Johnson
1984). Clark and colleagues (Clark et al. 1986; Clark and Ellison 1988,1989;
Clark et al. 1996) have used dispersed arrays of hydrophones to locate and
track vocalizing bowhead whales. These acoustic location data have led to
P.L. Tyack and c.w. Clark
and Vehrencamp 1998). Catchpole (1982) suggests that continuous singing,
lack of matched counter-singing between males, and lack of a singing
response to song playback are also diagnostic of a female attraction role
for song. Humpback whales often sing continually for hours, they do not
respond to the song of another male by immediately matching the sounds
produced by the male, nor do they respond to song playbacks by singing
themselves. These features are consistent with the hypothesis that humpback males sing in part to influence the mating choices of females. Humpback songs have several features that suggest that males are attending to
the songs of other males: they are acoustically elaborate, singers within a
population sing similar songs at anyone time, and males constantly change
their songs over the course of the breeding season. For singers to track all
these myriad changes, they must be attending to many subtle features of
the songs of other whales.
3.2.2 Balaenid Whales: Bowhead and Right Whales
Baleen whales other than humpback whales have also been reported to
produce reproductive advertisement displays. Bowhead whales, B. mysticetus, have been recorded producing songs as they migrate from their breeding grounds (Ljungblad et al. 1982; Clark 1988, 1991a; Wiirsig and Clark
1993). These whales spend their winter breeding season in arctic waters such
as the Bering Sea, where it is difficult to observe them, so we know little
about behavior during the peak of the breeding season. While the individual sounds that make up bowhead songs are somewhat similar to those of
humpbacks, bowhead songs have a simpler structure, consisting of a single
trill of repeated, multi-unit phrases followed by a trill of repeated, singleunit phrases. Bowhead songs are also shorter than humpback song, lasting
a minute or so. The songs of bowhead whales share an unusual feature with
the songs of humpback whales: they change from year to year. An unusual
feature of bowhead song is that it is composed of two voices that are harmonically unrelated yet often simultaneous. Figure 4.10 shows bowhead
songs of the Bering-Chukchi-Beaufort Seas population from four different
years recorded during the spring migration off Point Barrow, Alaska. The
communicative function of songs during migration is unknown. The following observations suggest that spring song of migrating whales may be a
vestige at the end of the winter breeding season: (1) this singing is only
recorded during the first weeks of the migration when the migration is dominated by adult males and small adults, (2) spring song is infrequent, and
(3) spring song is limited to bouts lasting only a few hours.
The great majority of sounds produced by bowhead whales during the
spring migration off Point Barrow, Alaska, are calls (Clark and Johnson
1984). Clark and colleagues (Clark et al. 1986; Clark and Ellison 1988,1989;
Clark et al. 1996) have used dispersed arrays of hydrophones to locate and
track vocalizing bowhead whales. These acoustic location data have led to